Systems and methods for estimating the length and position of a stent to be applied within a patient

ABSTRACT

The field of the invention relates to medical imaging systems, and more particularly to systems and methods for estimating the size and position of a stent or other medical device within a patient. In one embodiment, a medical imaging system includes an elongated tubular member having distal and proximal ends, configured to be inserted into a vessel of a patient, an imaging device coupled to the distal end of the elongated tubular member and configured to emit one or more energy pulses and receive one or more echo signals, and a console electrically coupled to the imaging device, wherein the console includes a computer-usable medium, electrically coupled to the imaging device, having a sequence of instructions which, when executed by a processor, causes said processor to execute a process including generating an image of the vessel, and providing a graphical representation of a stent to be overlaid onto the image.

FIELD OF THE INVENTION

The field of the invention relates to medical imaging systems, and moreparticularly to systems and methods for estimating the length andposition of a stent or other medical device to be applied within apatient.

BACKGROUND OF THE INVENTION

Intraluminal, intracavity, intravascular, and intracardiac treatmentsand diagnosis of medical conditions utilizing minimally invasiveprocedures are effective tools in many areas of medical practice. Theseprocedures are typically performed using imaging and treatment cathetersthat are inserted percutaneously into the body and into an accessiblevessel of the vascular system at a site remote from the vessel or organto be diagnosed and/or treated, such as the femoral artery. The catheteris then advanced through the vessels of the vascular system to theregion of the body to be treated. The catheter may be equipped with animaging device, typically an ultrasound imaging device, which is used tolocate and diagnose a diseased portion of the body, such as a stenosedregion of an artery. For example, U.S. Pat. No. 5,368,035, issued toHamm et al., the disclosure of which is incorporated herein byreference, describes a catheter having an intravascular ultrasoundimaging transducer.

FIG. 1 shows an example of an imaging transducer assembly 1 known in theart. The imaging transducer 1 is typically within the lumen 10 of aguidewire (partially shown), having an outer tubular wall member 5. Toobtain an image of a blood vessel, the imaging transducer assembly 1 maybe inserted into the vessel. The transducer assembly 1 may then rotatewhile simultaneously emitting energy pulses, e.g., ultrasound waves, atportions of the vessel from within the vessel and receiving echo orreflected signals.

Turning to FIG. 2, it is known in the art that an imaging console 20having a display screen, a processor and associated graphics hardware(not shown) may be coupled with the imaging transducer assembly 1 toform a medical imaging system 30. The imaging console 20 processes thereceived echo signals from the imaging transducer assembly 1 and formsimages of the area being imaged. To form the images, the imaging console20 draws multiple lines, known as “radial lines”, (not shown) on thedisplay screen that each correspond to an angular position of thetransducer assembly 1. The processor of the imaging console 20 assignsbrightness values to pixels of the lines based on magnitude levels ofthe echo signals received from the transducer assembly 1 at the angularpositions corresponding to the lines. A drawing that includes a largenumber of these radial lines results in an image such as anintravascular ultrasound (IVUS) image (not shown).

It is further known in the art to continually capture frames of IVUSimages while gradually withdrawing the transducer or catheter within avessel. The resulting stack of frames may be stored and manipulated bythe processor, and from these frames, a longitudinal image of the vesselmay be generated. In other words, a visualization of the vessel in aplane containing the long axis of the vessel may be rendered, whichallows the clinician to assess blockage at different locations along thelength of the vessel. For example, U.S. Pat. No. 5,830,145, issued toTenhoff, the disclosure of which is incorporated herein by reference,describes a system and method for generating longitudinal images of aregion of a blood vessel.

The resulting longitudinal image may be used to diagnose abnormalities,such as blockage, within the vessel. A typical treatment known in theart for such abnormalities is the use of one or more stents in theregion(s) of interest. Often times, determining the proper size (lengthand diameter) and position of the stent(s) to be applied within thepatient is a “trial and error” type process, which may increaseprocedure time and risk to the patient. Accordingly, an improved systemand method for delivering one or more stents would be desirable.

SUMMARY OF THE INVENTION

The field of the invention relates to medical imaging systems, and moreparticularly to systems and methods for estimating the size and positionof a stent or other medical device to be applied within a patient.

In one embodiment, a medical imaging system includes an elongatedtubular member having distal and proximal ends, configured to beinserted into a vessel of a patient, an imaging device coupled to thedistal end of the elongated tubular member and configured to emit one ormore energy pulses and receive one or more echo signals, and a consoleelectrically coupled to the imaging device, wherein the console includesa computer-usable medium, electrically coupled to the imaging device,having a sequence of instructions which, when executed by a processor,causes said processor to execute a process including generating an imageof the vessel, and providing a graphical representation of a stent orother medical device to be overlaid onto the image.

Other systems, methods, features and advantages of the invention will beor will become apparent to one with skill in the art upon examination ofthe following figures and detailed description. It is intended that allsuch additional systems, methods, features and advantages be includedwithin this description, be within the scope of the invention, and beprotected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better appreciate how the above-recited and other advantagesand objects of the inventions are obtained, a more particulardescription of the embodiments briefly described above will be renderedby reference to specific embodiments thereof, which are illustrated inthe accompanying drawings. It should be noted that the components in thefigures are not necessarily to scale, emphasis instead being placed uponillustrating the principles of the invention. Moreover, in the figures,like reference numerals designate corresponding parts throughout thedifferent views. However, like parts do not always have like referencenumerals. Moreover, all illustrations are intended to convey concepts,where relative sizes, shapes and other detailed attributes may beillustrated schematically rather than literally or precisely.

FIG. 1 is a cross-sectional side view of an imaging transducer assemblyknown in the art;

FIG. 2 is a block diagram of a medical imaging system known in the art;

FIG. 3 depicts a human heart as a potential site for use of the methodand apparatus disclosed herein;

FIG. 4 depicts an exploded view of a region of the coronary arterieshaving an IVUS catheter positioned in a region of interest;

FIG. 5 depicts a user interface for displaying a longitudinal medicalimage known in the art;

FIG. 6 depicts a user interface for displaying a longitudinal medicalimage in accordance with a preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The methods and systems disclosed herein are applicable to medicalimaging, such as ultrasound imaging, of vessels, such as the coronaryarteries as depicted in FIG. 3, or to any body cavity where the image isto be obtained over a region. With reference to FIG. 3, heart 99includes coronary arteries 98 which follow a tortuous path along thesurface of the heart. FIG. 4 shows an exploded view of curvature 97,having an IVUS catheter 21 disposed within a region of interest therein.Catheter 21 has distal end 22 and a proximal end (not shown), and isgenerally designed in accordance with imaging catheters known in theart. The catheter thus includes an intraluminal ultrasound imagingsystem, such as that shown in FIG. 1., capable of obtaining echographicimages of the surrounding of catheter tip 22. The imaging systemincludes transducer 23 and its associated electronics for displaying anechographic data set, e.g., obtained by scanning transducer 23 over a360-degree path 24 about distal tip 22 of catheter 21, or by a sectorscan which makes a 60 or 90 degree scan. In an alternative embodiment,transducer 23 is replaced-by a phased array as disclosed in Griffith etal., U.S. Pat. No. 4,841,977. Further, other imaging devices may beused, instead of, or in addition to imaging transducers, such as lightbased apparatuses for obtaining images through optical coherencetomography (OCT). Image acquisition using OCT is described in Huang etal., “Optical Coherence Tomography,” Science, 254, Nov. 22, 1991, pp1178-1181. A type of OCT imaging device, called an optical coherencedomain reflectometer (OCDR) is disclosed in Swanson U.S. Pat. No.5,321,501, which is incorporated herein by reference. The OCDR iscapable of electronically performing two- and three-dimensional imagescans over an extended longitudinal or depth range with sharp focus andhigh resolution and sensitivity over the range.

Scanning of the vessel interior is repeated many times during pull-backto obtain a plurality of echographic data sets taken at a sequence ofpositions 27 within vessel 98. In one embodiment, each echographic dataset obtained during pull-back comprises a transverse or cross-sectional(i.e., r-Θ)) image of the vessel at the point of the image, as shown inFIG. 4. An example of a cross-sectional image 120 is shown in FIG. 5. By“stacking” these images, a longitudinal image 105, i.e., an image alongthe longitudinal axis, or z axis, of the vessel may be generated, anexample of which is also shown in FIG. 5. Such an image is known in theart as a “cut-plane” image. The longitudinal image 105 may be rotatedalong the z axis to display the image 105 at different angles, Θ, untildesired features appear.

The longitudinal image 105 is typically generated by a software program,which may reside within the imaging console 20, shown in FIG. 2. Thesoftware program displays the image on a display device (not shown) ofthe imaging console 20. Turning to FIG. 5, the software program mayinclude a user interface 100. The user interface 100 includes a firstwindow 110, which displays a longitudinal image 105 of a vessel. Asmentioned above, the longitudinal image 105 comprises of a plurality ofr-Θ cross-sectional images obtained over time as the catheter 21 isbeing pulled back. Each of these r-Θ images may be regarded as frames120, and the longitudinal image 105 may be displayed as an animationsequence presenting each frame 120 sequentially. These frames 120 aretypically generated at a rate of approximately 30 frames/sec, and thecatheter 21 is typically pulled back at a speed of approximatelyone-half mm/sec. Thus, the frames 120 are typically displayed very closetogether.

The user interface 100 may include control elements that allow a user tocontrol the display of the longitudinal image 105. The control elementsmay include a playback element 130, a stop playback element 140, and anadjust cut-plane position element 125, which allows a user to rotate thelongitudinal image 105 along the z axis. Also included is a framecontrol 150 element that allows a user to scroll through the frames 120,backwards and forwards, and select the display of a particular frame 120within the sequence. The position of the user selected frame 120 withinthe sequence of the animation is known as the cursor position. The framecontrol 150 element includes a scrollbar button 155 that indicates thecursor position. The user interface 100 also includes a second window120, which displays the frame 120, or cross-sectional image,corresponding to the cursor position. The control elements may bebuttons, keys, sliders, scrollbars, virtual keys on a touch screen, orother user actuatable devices.

Generally, a clinician would analyze the image for abnormalities, and ifan abnormality requiring one or more stents were discovered in theimage, the clinician would visually estimate the length and position ofthe proper stent to be applied in the region of the abnormality. Oneapproach to facilitate the estimation is to provide a graphical toolthat allows a clinician to apply a graphical representation of a stent160 over the longitudinal image 105 being analyzed. The clinician may beable to graphically adjust the size of the stent 160 to a desired size.One approach may be to drag a mouse pointer over a corner of the stentto adjust the size; however, stent sizes are typically pre-defined andpre-packaged by stent manufacturers, and thus the variety of differentsizes may be limited. In such a case, it may be desirable to provide agraphical palette 165, or a predefined library, of one or morepre-defined stents with their sizes and other characteristics in theuser interface 100. Because the library is predefined with the necessarydimensions and characteristics of each stent, the clinician may simplyclick on or otherwise select the desired stent within the palette 165and drag the desired stent to a desired position on the longitudinalimage 105 to determine if the selected stent is appropriate. One ofordinary skill in the art may appreciate that additional sizes,characteristics, or devices may be added to the palette 165 or library.

After the clinician has established a desired location, or position, onthe longitudinal image 105 to place the stent 160, the clinician mayplace bookmarks in the image to record the desired location (preferably,one bookmark on each end of the location). The bookmarks essentiallyrecord the particular frames 120 that define the desired location withinthe longitudinal image 105. In addition, the graphical representation ofthe stent 160 may be transparent to maintain the visibility of thestructure of the image 105. Providing a clinician a graphical tool tosimulate the length and position of a stent within the image 105facilitates in the selection of the proper stent size and position priorto placing the actual stent, which are costly and permanent implants,within the area of interest.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Forexample, this invention is particularly suited for applicationsinvolving stents, but can be applicable for other medical devices. As afurther example, each feature of one embodiment can be mixed and matchedwith other features shown in other embodiments. Additionally andobviously, features may be added or subtracted as desired. Accordingly,the invention is not to be restricted except in light of the attachedclaims and their equivalents.

1. A medical imaging system comprising: an elongated tubular memberhaving distal and proximal ends, configured to be inserted into a vesselof a patient; an imaging device coupled to the distal end of theelongated tubular member and configured to emit one or more energypulses and receive one or more echo signals; and a console electricallycoupled to the imaging device, wherein the console includes a processorconfigured to execute a process including generating an image of thevessel and providing a graphical representation of a stent to beoverlaid onto the image.
 2. The medical imaging system of claim 1,wherein the imaging device comprises an ultrasound imaging transducerassembly.
 3. The medical imaging system of claim 1, wherein the image isa longitudinal image.
 4. The medical imaging system of claim 3, whereinthe longitudinal image is generated by stacking cross-sectional framesgenerated as the imaging transducer assembly is being pulled back withinthe vessel.
 5. The medical imaging system of claim 4, wherein thesequence of instructions further comprises generating a user interfaceto present the image of the vessel.
 6. The medical imaging system ofclaim 5, wherein the user interface provides controls that allow a userto playback the longitudinal image frame-by-frame.
 7. The medicalimaging system of claim 1, wherein the sequence of instructions furthercomprises providing a library of different stents from which a user canchoose to overlay onto the image of the vessel.
 8. The medical imagingsystem of claim 1, wherein a location of the graphical representation ofa stent may be adjusted by a user.
 9. The medical imaging system ofclaim 8, wherein the distal and proximal ends of a stent location may bebookmarked.
 10. A method for estimating the size, location, and positionof a stent to be applied within a vessel of a patient, comprising thesteps of: generating a longitudinal image of the vessel; and providing agraphical representation of a stent to be overlaid onto the image,wherein the graphical representation of the stent is transparent. 11.The method of claim 10, wherein the longitudinal image is generated bystacking cross-sectional frames generated as an imaging transducerassembly is being pulled back within the vessel.
 12. The method of claim11, further comprising generating a user interface to present the imageof the vessel.
 13. The method of claim 12, wherein the user interfaceprovides controls that allow a user to playback the longitudinal imageframe-by-frame.
 14. The method of claim 10, further comprising providinga user-defined library of stents of different sizes from which a usercan choose to overlay onto the image of the vessel.
 15. The method ofclaim 10, wherein a location of the graphical representation of a stentrelative to the vessel may be established by a user.
 16. The method ofclaim 15, wherein the location may be bookmarked.
 17. A system forestimating the size, location, and position of a stent to be appliedwithin a vessel of a patient, comprising: a means for generatinglongitudinal image of the vessel; and a means for providing a graphicalrepresentation of a stent to be overlaid onto the image.
 18. The systemof claim 17, wherein the longitudinal image is generated by stackingcross-sectional frames generated as an imaging transducer assembly isbeing pulled back within the vessel.
 19. The system of claim 18, furthercomprising a means for generating a user interface to present the imageof the vessel.
 20. The system of claim 19, wherein the user interfaceprovides controls that allow a user to playback the longitudinal imageframe-by-frame.
 21. The system of claim 17, further comprising a meansfor providing a library of stents of different sizes from which a usercan choose to overlay onto the image of the vessel.
 22. The system ofclaim 17, wherein a location of the graphical representation of a stentmay be established by a user.
 23. The system of claim 22, wherein thelocation may be bookmarked.
 24. A computer program product that includesa computer-usable medium having a sequence of instructions which, whenexecuted by a processor, causes said processor to execute a process forestimating the size, location, and position of a stent to be appliedwithin a vessel of a patient, comprising: generating an image of thevessel; and providing a graphical representation of a stent to beoverlaid onto the image.